Planar magnetrons have long been used by the semiconductor processing industry as sputtering devices to coat silicon wafers with various materials, for example, aluminum, during the manufacture of integrated circuits.
A sputtering device with a stationary planar magnetron is typically a high-rate sputtering device which represents an enormous improvement over devices based on diode sputtering or evaporative techniques. However, a sputtering device with a stationary planar magnetron has practical shortcomings, the most serious of which is that the plasma discharge erodes a narrow groove in the target. This localized erosion generates a non-uniform distribution of sputtered atoms which results in a deposition on a stationary semiconductor wafer having a non-uniform step coverage.
Numerous attempts, some partially successful, have been made to modify such a source to extend the target erosion and to make the distribution of sputtered atoms more uniform. For example, U.S. Pat. No. 4,444,643, which is incorporated herein by reference, describes as sputtering device which includes a mechanically rotated permanent magnet assembly. The rotation of the permanent magnet assembly causes erosion over a wider area of the target.
Special arrangements of magnets have also been suggested for producing more uniform erosion. One such arrangement is described in U.S. Pat. No. 4,872,964 entitled "Planar Sputtering Apparatus And Its Magnetic Source", which is incorporated herein by reference. The apparatus described in the above publication purports to achieve uniform erosion in the annular region between two concentric circles having a common center at the center of rotation of the magnet apparatus.
Japanese Patent Application publication (Kokai) No. 62-211,375, entitled "Sputtering Apparatus", published Mar. 11, 1986 describes another rotating sputtering apparatus, which purports to achieve, uniform erosion in an annular region which does not include the center of rotation.
Another approach for achieving uniform erosion in an annular region is described in U.S. patent application Ser. No. 355,713 entitled "Sputtering Apparatus With A Rotating Magnet Array Having A Geometry For Specified Target Erosion Profile" filed May 22, 1989 and assigned to the assignee hereof, which is incorporated herein by reference.
None of the above approaches is capable of achieving uniform erosion in a disk-like region by simple rotation of the magnet structure.